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Template Function of SDS-PVP Soft Cluster in the Synthesis of Ultrafine Nickel Powders

Author: RuanXiaoYun
Tutor: FangYun
School: Jiangnan University
Course: Chemical processes
Keywords: Ultrafine nickel powder Preparation Sodium dodecyl sulfate Polyvinylpyrrolidone soft template
CLC: TB383.3
Type: Master's thesis
Year: 2008
Downloads: 72
Quote: 2
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Abstract


Recently, Synthesis of nano-/ micro- particles in soft templates has received considerable attention. Studies on the templates of surfactant and macromolecule are the most active research fields. People wish to control the size, morphology and structure of the materials basing on the limited space and controllable effect of the template composition.In this paper, the interaction between nickel ions and sodium dodecyl sulfate(SDS)- polyvinylpyrrolidone(PVP) cluster was investigated by means of surface tension and Zeta potential method. The results showed that the existence of nickel ions would not destroy the formation of cluster by PVP and SDS bound-micelle. Theγ-lgc curves of NiCl2-SDS-PVP systems still held two critical concentrations: the first critical concentration (c1) and the second critical concentration (c2). The increase of nickel ions’concentration favored the formation of bound-micelle, and making surface tension decreased further. In the meantime, c1 decreased while c2 increased with ever-increasing level of nickel ions. With the increasing concentration of PVP, the first critical concentration c1 was basically unchanged while the second critical concentration c2 increased correspondingly. Therefore, the clusterization boundary of SDS-PVP cluster extended, and the controllable range of soft template in preparing ultrafine nickel powders increased accordingly.Ultrafine nickel powders were prepared from nickel chloride reduced by hydrazine in aqueous solution of sodium dodecyl sulfate (SDS)-polyvinylpyrrolidone (PVP). SEM proof showed that the reduced products were sphere with special needle-like morphology which average diameters were about 400-800 nm. XRD displayed that the spherical ultrafine nickel powders were self-assembled into by the primary pure crystalline nanonickel of face centric structural (fcc) with the mean crystal size about 10 nm, and grown preferentially along (111) lattice plane. The process that the primary pure crystalline nanonickels self-assembled into the ultrafine nickel powders in virtue of the coupling of PVP chain was clearly observed by TEM. Thus we get the following conclusions: In the process of preparing ultrafine nickel powders, the primary pure crystalline nanonickels similar to the size of soft template developed in the first microreactor of SDS bound micelle, then closed with each other and assembled orderly in virtue of the coupling of PVP chain, self-assembled into ultrafine nickel powders at last. It showed that the SDS-PVP cluster with structure of two-ply soft template played a particular role of twice induced self-assemble function in the synthesis of ultrafine nickel powders. The composition of the SDS-PVP mixing system had great influence on the size and shape of ultrafine nickel powders .At a certain concentration, the size of the primary pure crystalline nanonickel and the secondary ultrafine nickel powders showed a decreased trend with the higher concentration of SDS or PVP. It was revealed a promising possibility of a size and morphology controllable production of the ultrafine nickel particles by adjusting the composition of SDS and PVP. UV-Vis spectra were employed to monitor the reaction process and investigate the optical properties of the system. It was found that the absorption peak in the UV-Vis spectras of nickel sols was blue-shifted with the decreasing of ultrafine nickel powders’average diameter by studying the effect of SDS, PVP and NiCl2’ concentration.

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